The present invention relates to an improvement in a method and an apparatus for performing surface treatment of a tool by interposing working fluid between an electrode and the tool and by causing discharge to occur to use the energy of the discharge so as to form a hard coating film at the tip of the tool.
A general machining operation including a machining operation of a type using a mold has frequently used a very hard material having considerable toughness. In the foregoing case, the lifetime of the tool is excessively shortened, causing productivity to deteriorate. Therefore, if the lifetime of the tool comes to an end, the tip of the tool is again ground and modified by a machine for grinding the tool. Thus, reuse of the tool is permitted. Since the re-grinding operation causes the hardened portion of the surface of the tip to be separated or removed, a re-hardening process must be performed in order to improving the hardness of the tip.
When the process for hardening the surface of the tip of the tool is performed by chemical evaporation or physical evaporation, an excessively great cost is required. What is worse, the foregoing evaporation process must be entrusted to a special contractor. Thus, there arise problems in that a great cost and excessively long time are required to complete the process and that a long delivery times runs.
As a method and an apparatus for performing surface treatment of a tool using a discharge process, a technique disclosed in Japanese Patent Laid-Open No. 7-112329 is known. The surface treatment for a tool, which is the foregoing conventional technique, will now be described. FIG. 8 is a diagram showing the overall structure of the apparatus for subjecting a tool to surface treatment. Referring to FIG. 8, reference numeral 201 represents a tool, such as an end mill or drill, which must be subject to surface treatment. Reference numeral 202 represents a green compact block obtained by molding powder of a material for forming a hard coating film. The material for forming the hard coating film is obtained by sinter-molding a material prepared by mixing powder of Co (cobalt) into Wxe2x80x94C (tungsten-carbide). Reference numeral 203 represents a main shaft for moving the tool 201 in the vertical direction (direction Z). Reference numeral 204 represents a working tank in which the green compact block 202 is secured and which is filled with working fluid 205. Reference numeral 206 represents an electric power source for applying voltage between the tool 201 and the green compact block 202. Reference numeral 207 represents an interpole detecting unit for detecting bath voltage or short circuit between the tool 201 and the green compact block 202. Reference numeral 208 represents a control unit for controlling relative movement velocity between the tool 201 and the green compact block 202 in accordance with a result of detection performed by the interpole detecting unit 207. Reference numeral 209 represents a Z-axis drive unit for moving the main shaft 203 in the direction Z together with the tool 201 by discharge. Reference numeral 210 represents an X-axis drive unit for moving the working tank 204 in the direction X together with the green compact block 202. Reference numeral 211 represents a Y-axis drive unit for moving the working tank 204 in the direction Y together with the green compact block 202. Reference numeral 212 represents a rotating unit for rotating the tool 201.
The operation of the conventional apparatus for performing surface treatment of a tool will now be described. The tool 201 held by the main shaft 203 is rotated by the rotating unit 212. The X-axis drive unit 210, the Y-axis drive unit 211 and the Z-axis drive unit 209 relatively move the tool 201 and the green compact block 202 so that an operation for grinding the green compact block 202 is performed. When the tool 201 is the end mill, grinding is performed in the direction of the side surfaces (that is, the directions X and Y). When the tool 201 is the drill, grinding is performed in the direction Z. At this time, voltage for performing a discharging process has been applied to a space between the tool 201 and the green compact block 202 from the electric power source 206. Therefore, suspension of the contact between the tool 201 and the green compact block 202 owing to proceeding of the grinding work causes discharge to occur at the gap between the two elements. Powder of the hard coating film material (Wxe2x80x94C) floats in the gap existing between the tool 201 and the green compact block 202 owing to the operation for grinding the green compact block 202. Therefore, Wxe2x80x94C powder is mixed into the surface of the tip of the tool 201. Hence it follows that proper control of the feed speed of the tool 201 enables a continuous operation to be performed such that grinding and discharge are repeated. As a result, a uniform hard coating film is formed on the tip of the tool. That is, according to the foregoing disclosure, the method is disclosed with which a discharging process is performed while the block containing the material for the hard coating film is being ground so that the surface treatment of the tool is performed by the discharging process.
The foregoing method has a structure formed by combining the two contrary machining processes which are the grinding process which is performed such that the block including the material for the hard coating film and the tip of the tool are made contact with each other and the discharging process in which the block including the material for the hard coating film and the tip of the tool are free from contact. Therefore, the machining operation cannot stably be performed. Moreover, a uniform hard coating film cannot be formed on the tip of the tool. Moreover, the tip of the tool wears away by friction with the block including the material for the hard coating film during the grinding process and the tip of the tool becomes dull owing to a concentration of discharge during the discharging process. Therefore, a process is required to polish the tip of the tool on which the hard coating film has been formed.
To radically overcome the above-mentioned problems, an object of the present invention is to provide a method and an apparatus for performing surface treatment of a tool which are capable of automatically performing a surface treatment of a tool incorporating a main cutting edge having an arbitrary angle by using a discharging process, stably and quickly obtaining a uniform hard coating film having high hardness and exhibiting excellent adhesiveness with a low cost, automatically modifying electrodes thereof and permitting unmanned operation for a long time.
According to a first aspect of the present invention, there is provided a method of performing surface treatment of a tool, comprising the steps of: securing the first electrode to an indexing unit which indexes the angle of the first electrode; changing the first tool which is connected and secured to the main shaft which is moved vertically to a second tool or a second electrode by an automatic tool changing unit when an operation for modifying the surface of the first electrode is performed; modifying the first electrode into a predetermined shape by a machining operation which is performed by the second tool or by a discharging operation which is performed by the second electrode; changing the second tool or the second electrode connected and secured to the main shaft to the first tool by the automatic tool changing unit; indexing the first electrode to a predetermined angle of rotation by the indexing unit; causing discharge to occur while relatively moving the tip of the first tool along the surface of the first electrode such that the tip is made to be opposite to the surface of the first electrode while a predetermined distance is being maintained; and forming a hard coating film on the tip of the first tool.
According to a second aspect of the present invention, there is provided a method of performing surface treatment of a tool having a structure of the method of performing surface treatment of a tool which is the first aspect of the present invention, wherein the outside shape of the first electrode secured to the indexing unit is formed into a polygonal shape.
According to a third aspect of the present invention, there is provided a method of performing surface treatment of a tool having a structure of the method of performing surface treatment of a tool which is the first aspect of the present invention, wherein the outside shape of the first electrode secured to the indexing unit is formed into a circular arc shape.
According to a fourth aspect of the present invention, there is provided a method of performing surface treatment of a tool having a structure of the method of performing surface treatment of a tool which is the first aspect of the present invention, wherein a circular-arc electrode and a polygonal electrode are arranged so as to be secured to the indexing unit.
According to a fifth aspect of the present invention, there is provided a method of performing surface treatment of a tool comprising the steps of: securing the first electrode to an indexing unit which indexes the angle of the first electrode; connecting and securing the first tool to a first main shaft which is moved vertically; modifying the first electrode to a predetermined shape by a machining operation which is performed by a second tool or a discharging operation which is performed by a second tool when an operation for modifying the surface of the first electrode is performed, the second tool and the second electrode being connected and secured to a second main shaft which is provided individually from the first main shaft and which is vertically moved; indexing the first electrode to a predetermined angle of rotation by the indexing unit; causing discharge to occur while relatively moving the tip of the first tool along the surface of the first electrode such that the tip is made to be opposite to the surface of the first electrode while a predetermined distance is being maintained; and forming a hard coating film on the tip of the first tool.
According to a sixth aspect of the present invention, there is provided a method of performing surface treatment of a tool having a structure of the method of performing surface treatment of a tool which is the fifth aspect of the present invention, wherein the outside shape of the first electrode secured to the indexing unit is formed into a polygonal shape.
According to a seventh aspect of the present invention, there is provided a method of performing surface treatment of a tool having a structure of the method of performing surface treatment of a tool which is the fifth aspect of the present invention, wherein the outside shape of the first electrode secured to the indexing unit is formed into a circular arc shape.
According to an eighth aspect of the present invention, there is provided a method of performing surface treatment of a tool having a structure of the method of performing surface treatment of a tool which is the fifth aspect of the present invention, wherein a circular-arc electrode and a polygonal electrode are arranged so as to be secured to the indexing unit.
According to a ninth aspect of the present invention, there is provided an apparatus for performing surface treatment of a tool comprising: an indexing unit for supporting the first electrode and indexing the angle of the first electrode; a main shaft which supports a rotating unit and which is moved in a vertical direction; a first tool supported by the rotating unit; accommodating means which is capable of accommodating at least either of a modifying tool or a modifying electrode and a tool which is a material which must be processed; a second modifying tool or a second modifying electrode accommodated in the accommodating means; an automatic tool changing unit for automatically changing the tool or the electrode supported by the rotating unit to the tool or the electrode accommodated in the accommodating means; an X-axis drive unit, a Y-axis drive unit and a Z-axis drive unit for relatively moving the main shaft and the first electrode in directions X, Y and Z, wherein the first tool supported by the rotating unit is changed to the second tool or the second electrode accommodated in the accommodating means by the automatic tool changing unit when an operation for modifying the surface of the first electrode is performed; the first electrode is modified into a predetermined shape by a machining operation which is performed by the second tool or by a discharging operation which is performed by the second electrode; the second tool or the second electrode is changed to the first tool by the automatic tool changing unit; the first electrode is indexed to a predetermined angle of rotation by the indexing unit; discharge is caused to occur while the tip of the first tool is being moved relatively along the surface of the first electrode such that the tip is made to be opposite to the surface of the first electrode while a predetermined distance is being maintained by the X-axis drive unit, the Y-axis drive unit and the Z-axis drive unit; and a hard coating film is formed on the tip of the first tool.
According to a tenth aspect of the present invention, there is provided an apparatus for performing surface treatment of a tool having a structure of the apparatus for performing surface treatment of a tool which is the ninth aspect of the present invention, wherein the outside shape of the first electrode secured to the indexing unit is formed into a polygonal shape.
According to an eleventh aspect of the present invention, there is provided an apparatus for performing surface treatment of a tool having a structure of the apparatus for performing surface treatment of a tool which is the ninth aspect of the present invention, wherein the outside shape of the first electrode secured to the indexing unit is formed into a circular arc shape.
According to a twelfth aspect of the present invention, there is provided an apparatus for performing surface treatment of a tool having a structure of the apparatus for performing surface treatment of a tool which is the ninth aspect of the present invention, wherein a circular-arc electrode and a polygonal electrode are arranged so as to be secured to the indexing unit.
According to a thirteenth aspect of the present invention, there is provided an apparatus for performing surface treatment of a tool, comprising: an indexing unit for supporting the first electrode and indexing the angle of the first electrode; a first main shaft which supports a rotating unit and which is moved in a vertical direction; a first tool supported by the rotating unit; a second tool or a second electrode connected and secured to a second main shaft which is provided individually from the first main shaft and which is moved in a vertical direction; an X-axis drive unit, a Y-axis drive unit and a Z-axis drive unit for relatively moving the first main shaft and the first electrode in directions X, Y and Z, wherein the first electrode is modified into a predetermined shape by a machining operation which is performed by the second tool or by a discharging operation which is performed by the second electrode when modification of the surface of the first electrode is performed; the first electrode is indexed to a predetermined angle of rotation by the indexing unit; discharge is caused to occur while relatively moving the tip of the first tool along the surface of the first electrode such that the tip is made to be opposite to the surface of the first electrode while a predetermined distance is being maintained by the rotating unit, the Xaxis drive unit, the Y-axis drive unit and the Z-axis drive unit; and a hard coating film is formed on the tip of the first tool.
According to a fourteenth aspect of the present invention, there is provided an apparatus for performing surface treatment of a tool having a structure of the apparatus for performing surface treatment of a tool which is the thirteenth aspect of the present invention, wherein the outside shape of the first electrode secured to the indexing unit is formed into a polygonal shape.
According to a fifteenth aspect of the present invention, there is provided a n apparatus for performing surface treatment of a tool having a structure of the apparatus for performing surface treatment of a tool which is the thirteenth aspect of the present invention, wherein the outside shape of the first electrode secured to the indexing unit is formed into a circular arc shape.
According to a sixteenth aspect of the present invention, there is provided an apparatus for performing surface treatment of a tool having a structure of the apparatus for performing surface treatment of a tool which is the thirteenth aspect of the present invention, where in a circular-arc electrode and a polygonal electrode are arranged so as to be secured to the indexing unit.
Since the present invention is structured as described above, the following effects can be obtained.
The method of performing surface treatment of a tool according to the first aspect of the present invention enables a tool incorporating a main edge having an arbitrary angle to automatically be subjected to surface treatment using a discharging operation. Moreover, a coating film having high hardness and exhibiting excellent adhesiveness can quickly be obtained with a low cost. In addition, the electrode can be modified by an automatic operation. The machining operation can be continued for a long time and a unmanned system can be realized.
The method of performing surface treatment of a tool according to the second aspect of the present invention attains similar effects to those obtainable from the first aspect of the present invention. Since a multiplicity of surfaces of electrodes each of which is formed into a polygonal shape can be used, continuous working duration can be elongated. Therefore, the operating rate and productivity can be improved. Moreover, the cost of the electrode can be reduced.
The method of performing surface treatment of a tool according to the third aspect of the present invention attains similar effects to those obtainable from the first aspect of the present invention. Moreover, a discharging operation of a tip of a ball end mill or the like having a free curved surface can easily be performed. In addition, the electrode can easily be manufactured.
The method of performing surface treatment of a tool according to the fourth aspect of the present invention attains similar effects to those obtainable from the first aspect of the present invention. Since change of the electrode is not required if the type of the tool is changed, the continuous working duration can be elongated. Therefore, the operating rate and productivity can be improved.
The method of performing surface treatment of a tool according to the fifth aspect of the present invention attains similar effects to those obtainable from the first aspect of the present invention. Moreover, the structure of the main shaft can be formed into a structure for performing only indexing. Thus, the number of times the tool is changed can be decreased. Thus, the productivity can be improved.
The method of performing surface treatment of a tool according to the sixth aspect of the present invention attains similar effects to those obtainable from the fifth aspect of the present invention. Since a multiplicity of surfaces of electrodes each of which is formed into a polygonal shape can be used, continuous working duration can be elongated. Therefore, the operating rate and productivity can be improved. Moreover, the cost of the electrode can be reduced.
The method of performing surface treatment of a tool according to the seventh aspect of the present invention attains similar effects to those obtainable from the fifth aspect of the present invention. Moreover, a discharging operation of a tip of a ball end mill or the like having a free curved surface can easily be performed. In addition, the electrode can easily be manufactured.
The method of performing surface treatment of a tool according to the eighth aspect of the present invention attains similar effects to those obtainable from the fifth aspect of the present invention. Since change of the electrode is not required if the type of the tool is changed, the continuous working duration can be elongated. Therefore, the operating rate and productivity can be improved.
The apparatus for performing surface treatment of a tool according to the ninth aspect of the present invention attains similar effects to those obtainable from the first aspect of the present invention.
The apparatus for performing surface treatment of a tool according to the tenth aspect of the present invention attains similar effects to those obtainable from the ninth aspect of the present invention. Since a multiplicity of surfaces of electrodes each of which is formed into a polygonal shape can be used, continuous working duration can be elongated. Therefore, the operating rate and productivity can be improved. Moreover, the cost of the electrode can be reduced.
The apparatus for performing surface treatment of a tool according to the eleventh aspect of the present invention attains similar effects to those obtainable from the ninth aspect of the present invention. Moreover, a discharging operation of a tip of a ball end mill or the like having a free curved surface can easily be performed. In addition, the electrode can easily be manufactured.
The apparatus for performing surface treatment of a tool according to the twelfth aspect of the present invention attains similar effects to those obtainable from the ninth aspect of the present invention. Since change of the electrode is not required if the type of the tool is changed, the continuous working duration can be elongated. Therefore, the operating rate and productivity can be improved.
The apparatus for performing surface treatment of a tool according to the thirteenth aspect of the present invention attains similar effects to those obtainable from the fifth aspect of the present invention.
The apparatus for performing surface treatment of a tool according to the fourteenth aspect of the present invention attains similar effects to those obtainable from the thirteenth aspect of the present invention. Since a multiplicity of surfaces of electrodes each of which is formed into a polygonal shape can be used, continuous working duration can be elongated. Therefore, the operating rate and productivity can be improved. Moreover, the cost of the electrode can be reduced.
The apparatus for performing surface treatment of a tool according to the fifteenth aspect of the present invention attains similar effects to those obtainable from the thirteenth aspect of the present invention. Moreover, a discharging operation of a tip of a ball end mill or the like having a free curved surface can easily be performed. In addition, the electrode can easily be manufactured.
The apparatus for performing surface treatment of a tool according to the sixteenth aspect of the present invention attains similar effects to those obtainable from the thirteenth aspect of the present invention. Since change of the electrode is not required if the type of the tool is changed, the continuous working duration can be elongated. Therefore, the operating rate and productivity can be improved.